Well of course if there are dual primaries then you would have to wire them appropriately, but in those cases the instructions are pretty clear I think. But in the case of transformers with a single primary (like any of the Hammond 270 series from my experience, or single primary trafos from SumR) it doesn't matter which way you wire them.
Here's Hammond's wiring diagram for the 270 series.
And Here's the 370 series: